Effect of Graphite Matrix on Property of Silicon/Carbon Composite Anode Material for Lithium-Ion Battery

Abstract

Nano-silicon carbon coated and combined with different graphite matrixes was synthesized by ball milling，and spray dying-pyrolysis methods. The physical properties of Si/C composites were detected by X-ray diffraction（XRD），scanning electron microscopy（SEM），and all composites were completely coated by a carbon layer. Their electrochemical performances were studied by galvanostatic cycle and electrochemical impedance spectra. These analyses show that the discharge specific capacity of composited anode based on expanded graphite exhibits the best comprehensive electrochemical performance such as cycle stability and initial charge/discharge efficiency among various composites，owing to the co-effect of expanded graphite and amorphous carbon layer as the structural stabilizer and conductive additives to prevent the volume change and enhance the electronic conductivity of the composites. The discharge specific capacity is 700.9 mAhg-1 at a current density of 100mAg-1，initial charge/discharge efficiency is 77.4%. After 30 cycles，the capacity retention rate can reach 87.7%.